This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Epithelial-mesenchymal transition (EMT) is a process in which epithelial cells lose cell adhesion and gain invasive and motile properties. The EMT program has been implicated in tumor metastasis. Although this process has been well characterized in cultured cells in vitro, the evidence of its occurrence in vivo is still lacking. Three-dimensional mammary organotypic cultures have been shown to closely model in vivo mammary epithelial cell biology. However, these studies were performed predominantly on culture cell lines and lack some features of in vivo mammary gland. Our goal is to adapt the organotypic model to our system using primary cells isolated from inducible transgenic mice to study EMT in 3D culture in real-time.